I just got back from a hike in the Olympic Mountains and I came across something that I have never noticed before.  It was a small bronze disk maybe three or four inches across in diameter and it was set in a rock at about the highest point of the peak I hiked to.  I asked my boyfriend about it and he told me it was a survey monument and that they were found all over the country and were used as a tool by surveyors for creating maps.  He pulled out his topographical map and sure enough it had several benchmarks on it.  I guess you learn something new every day.